Conventional ocean thermal energy conversion (OTEC) systems generally fall into three categories; first, a closed-cycle OTEC system 100 for generating electricity as illustrated in FIG. 1; second, an open-cycle OTEC system 200 for generating electricity as a primary product and fresh water as a secondary product as illustrated in FIG. 2; and third, a hybrid-cycle OTEC system 300 for generating electricity as a primary product and desalinated water as a secondary product, illustrated in FIG. 3. Each of these conventional OTEC systems will be discussed below in detail.
As illustrated in FIG. 1, a working fluid, which is contained within the closed cycle, is pumped by a liquid pump 102 into evaporator 104, where heat from a warm water intake is transferred from the warm water to the working fluid to generate a working fluid vapor. The warm water exiting the evaporator 104 is discharged to the sea. The working fluid vapor enters a turbogenerator 106 in order to generate electricity by conventional techniques. The working fluid vapor exits the turbogenerator 106 and is condensed in condenser 108 utilizing cold sea water as a heat sink. The condensed working fluid is then fed back to the feed pump in order to complete the closed cycle.
The open-cycle OTEC system 200 illustrated in FIG. 2 includes a flash evaporator 202 for receiving a warm sea water intake and outputting steam. Further, a pump 204 pumps a warm sea water discharge out of the flash evaporator 202. The steam output from the flash evaporator 202 is input to turbine 206 which is connected to generator 208 in order to generate electricity by conventional techniques. Steam exits the turbine 206 and is input to condenser 210. The conventional open-cycle OTEC system 200 utilizes a surface condenser and a direct contact condenser. A surface condenser keeps the two fluids (sea water and pure water) separate while a direct contact condenser does not. A majority of the steam exiting the turbine 206 is provided to a direct contact condenser in the conventional open-cycle OTEC system 200, in order to generate electricity. The conventional open-cycle OTEC system 200 utilizes a surface condenser to condense a small percentage of the steam generated by the turbine 206 into fresh water utilizing cold sea water as a heat sink. A cold sea water discharge is pumped out of the condenser 210 by a pump 212. The non-condensible exhaust system 212, removes non-condensible gases and a portion of the steam from the steam output from the turbine 206. In the open- cycle OTEC system 200 described above, the generation of electricity by the turbine 206 and generator 208 is the primary product and the fresh desalinated water output from the condenser 210 is the secondary product.
The hybrid-cycle OTEC system 300 illustrated in FIG. 3 includes an evaporator system 302 into which warm sea water is input, of which a small fraction, vaporizes in a vacuum flash evaporator 304. The vapor condenses on an ammonia evaporator 306, which contains ammonia liquid, pumped from pump 308. The vapor from the flash evaporation system 302 condenses on the ammonia evaporator 306, producing desalinated water. The ammonia vapor is input to an ammonia turbine/generator 310 in order to generate electricity by conventional techniques. The ammonia vapor is then condensed in an ammonia condenser 312. The recondensed ammonia is recycled to the pump 308 to complete the closed portion of the hybrid-cycle OTEC system 300.
Both the closed cycle and open cycle OTEC systems discussed above utilize separate evaporators and condensers. Further the hybrid cycle OTEC system discussed above utilizes a conventional evaporator system 302. The improved OTEC system of the present application includes a novel combined evaporator/condenser in contrast to the three above-identified systems. The combined evaporator/condenser further includes a plurality of evaporator spouts and a mist eliminator. The OTEC system of the present application further maintains a constant low pressure over each of the plurality of evaporator spouts. The OTEC system of the present application also generates fresh water as a primary product. The OTEC system of the present application generates only enough electricity, as a secondary product, to operate the OTEC system itself.